I tried the tactic below, but it didn't resolve the issue. When I do it, it sounds (feels?) like air is coming out of my left ear but not my right.

Do I have Eustachian tube dysfunction? Will this go away or do I need to seek medical attention?

Pop Your Ears by Holding Your Nose
One of the most recommended ways to pop your ears is by holding your nose and blowing out. First, take a breath. Then close your mouth and nostrils with your fingers. Lightly blow out against the pressure. This should make your ears pop.